Expandable shelf



FIG. 1 is a top left front perspective view of an expandable shelf of the present design;

FIG. 2 is a top right rear perspective view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a bottom view thereof;

FIG. 5 is a right side view thereof, the left side view being identical thereto;

FIG. 6 is a front view thereof; and,

FIG. 7 is a back view thereof. 

The ornamental design for “expandable shelf,” as shown and described. 